The present invention relates to a composition for use in removing the membrane from concrete and etching the concrete in preparation for coating. More particularly the present invention provides a system for membrane removal and/or etching concrete.
It is well recognized that concrete should be etched prior to applying coatings such as polyurethane and the like. In the past concrete has been etched by first treating the surface with an acid composition such as muratic acid. The acid step is then followed by a neutralization, for example, using a sodium hydroxide solution. The neutralized materials are then lifted and the surface dried. Such prior etching processes have been very time consuming in view of the multiple steps. Also, such prior processes have been somewhat difficult for nontrained personnel to carry out since the acid tends to continue to etch until neutralized thus limiting the amount of surface which can be treated with the acid step before going back and neutralizing the acid. Moreover the further step of water washing and picking up the residues further extends the time required for etching concrete. The present invention overcomes such disadvantages by providing a single step membrane remover/etchant system which may be applied by a machine which simultaneously applies water and also picks up the residues or by well known manual methods.
The usual practice in pouring concrete surfaces such as floors is to apply a membrane to the surface. The membrane holds in moisture thus assuring complete curing of the concrete. Illustrative materials used to form the curing membrane are thin coatings (e.g. continuous films of 1 to 3 mils.) of chlorinated rubbers, oleo resins, acrylic resins and a combination of rubber and epoxy resin. Of course the membrane must be removed before the concrete can be etched. In the past membranes have been removed by sand blasting. Sand blasting however requires additional equipment and the sand blasting often results in an uneven surface due to eating away of softer areas of the concrete. Use of solvents to remove the membrane has been found to be the more acceptable method. Solvent removal of the membrane has its own problems and disadvantages. For example, solvent removal requires substantial additional time. Time for applying the solvent, time for the solvent to act, time for picking up the solvent and membrane materials, time for flushing the surface with water and time for the surface to dry enough (e.g. Delmhorst Moisture Meter reading of 20 or lower) to permit application of the finish coating material. Of course the concrete must also be etched.
The present invention overcomes the difficulties encountered in prior processes and provides a single process to both remove the membrane and etch the concrete.